KI Dual field phase referencing mode

This page give the details for the Dual Field Phase Referencing (DFPR) mode, which is available for shared-risk observations in 2011A.

To maximize the science, performance characterization and engineering benefits of TAC-allocated science during the DFPR 2011A shared-risk availability, science teams are strongly encouraged to collaborate with the NSF-funded ASTRA development team throughout the science process from planning to publication (contact Julien Woillez, jwoillez at keck.hawaii.edu for more information about ASTRA). To recognize their contribution, publications based on 2010B DFPR data are strongly encouraged to include ASTRA team co-authors.

In DFPR, one fringe tracker is locked on a bright reference star, stabilizing a second fringe tracker which is tracking a much fainter science target. The star used by the AO system can be the bright reference star (scenario 1), or a third star, as described below. Angle tracking is done separately for the reference and targets stars. Currently fringe tracking is at K band, and angle tracking is at H band.

Proposals for DFPR mode MUST include the following items(note that the PI is responsible for identifying appropriate reference and calibrator objects as part of the proposal phase):

1. The reference star and target magnitudes and separations. The limits for these quantities are given below.
2. A calibrator pair for each target with magnitudes and separations. The sensitivity and separation parameters for the calibrator pair must follow reference star case 1, given below.
3. A paragraph describing the science which would be done in regular K-mode (K<10.3) if DFPR mode is not available.

In DFPR observing, observations of the calibrator pair will be interleaved with the target/reference pair as in standard V2 observing. The observing efficiency is expected to be 3 scans/hr. The expected V2 accuracy is 0.05, although this has not been fully demonstrated on sky.

Sensitivity limits:

• Reference star: Two scenarios are supported for the reference star:
  1. Same star for AO and fringe tracking.

     AO:                  R mag < 12
     Angle tracking:      H mag < 13
     Fringe tracking:     K mag < 8
     Distance to target:  5 to 25 arcsec
     

  2. Different stars for AO and fringe tracking.
     • AO reference star

       AO:                  R mag < 12
       Distance to target 
       and fringe reference 
       star:                < 35 arcsec 
       

     • Fringe tracking reference star:

       Angle tracking:      H mag < 13
       Fringe tracking:     K mag < 8
       Distance to target:  5 to 15 arcsec 
       

• Science target:

  Angle tracking:     H mag < 13
  Fringe tracking:    K < 12.3 if fringe tracking reference is within 15 arcsec
                      K < 11.3 if fringe tracking reference is within 25 arcsec
  

• Note that these sensitivities are for unresolved sources, see Table 1 on the V2 sensitivities page for the reduction in sensitivity for a resolved source.

The sky coverage and delay line constraints are the same as for the standard V2 modes.

Return to the KI V2 sensitivity page.

last updated: August 3, 2010